Taste represents an important factor in the decision to ingest substances, including alcohol. Attempts to prevent alcohol consumption in the course of therapy for alcoholics would be facilitated if one could render the taste of alcohol as aversive. Naltrexone, an opiate receptor blocker currently used for treatment of alcoholism, appears to have such properties for rats. Rats given naltrexone treatment respond to alcohol is if it were aversive or less palatable, as indicated by taste reactivity tests. Rats given naltrexone treatment respond to alcohol as if it were aversive or less palatable, as indicated by taste reactivity tests. In addition, alcohol consumption is reduced following acute naltrexone treatment when rats are given restricted fluid access. In the present proposal, we will examine further the hypothesis that naltrexone alters the paste perception of alcohol solutions in rats, specifically making it more aversive tasting. Taste reactivity (stereotyped mouth and tongue movements in addition to certain body movements) provides one with a quantitative measure of the hedonic value or palatability of taste solutions. We will examine both random-bred rats and selected lines of rats bred for high-alcohol consumption (high alcohol drinking or HAD rats from Indiana University, alcohol preferring or AA rats from Finland). The effects of low doses of naltrexone on alcohol taste reactivity will be examined in the first experiment. The next two experiments will determine the specificity of naltrexone by testing its effects on taste reactivity to several taste solutions and several alcohol concentrations. The following two experiments involve HAD and AA rats to determine if naltrexone can shift their taste reactivity to a more aversive sequence (and to decrease alcohol consumption under restricted access tests). An additional experiment will ascertain whether naltrexone has the same effect effects on taste reactivity for alcohol-naive versus alcohol- familiar rats. In the last three experiments (involving outbred, HAD, and AA rats, respective), the effects of chronic naltrexone on concurrent alcohol taste reactivity and alcohol consumption will be determined. The ultimate goal of the project is to characterize the taste processes that are affected by naltrexone, a treatment that has show promise for reducing alcohol consumption and preventing future release in humans. It is believed that an agent that can render the taste of alcohol as aversive and reduce its euphoric effects will be more efficacious in discouraging further consumption than either alone. This would represent an important new aspect for the clinical treatment of alcohol use and abuse.